We have all experienced it. Forgetting something, miscalculating, or having lower efficiency. Regardless of the reason, instead of accepting what you have, here are two simple ways to correct a high or low original gravity (OG).
Once you realize that you have missed your OG, you are faced with the problem of what to do with your batch. Fortunately, adjusting the OG of the wort as it goes into the fermenter is not difficult. You can achieve this by adding water or dry malt extract (DME). It is always helpful to keep a couple of pounds of light DME on hand for such situations.
If your gravity is too low, use the following calculation to add DME:
Determine the difference between your target OG and actual OG, then multiply it by 1000. For example, if your target is 1.056 but you have measured 1.048, the calculation would be (1.056-1.048) x 1000 = 8 points. Remember to make any necessary temperature corrections.
In this case, we need to increase our gravity by 8 points, which means we need to add 8 points per gallon of dry malt extract (DME) equivalent. Assuming a batch size of 5 gallons, we would require a total of 40 points of DME.
DME has a potential of 1.046, meaning it contributes 46 points per pound added. Therefore, we simply divide the 40 points by 46, resulting in 0.9 lbs of DME to add.
If the gravity is too high, dilute it by adding boiled or sterile water:
This time let’s assume our target OG was 1.056, but we overshot and measured a gravity of 1.064 for a 5-gallon batch. We can use the principle that the product of the number of points and volume should remain constant during dilution.
Starting with our initial gravity of 1.064, which is equivalent to 64 gravity points, and multiplying it by our original volume of 5 gallons, we get 64 x 5 = 320 points.
Next, we divide by our target points, which is 1.056 (56 gravity points), to calculate the target volume: 320 / 56 = 5.71 gallons.
Since we started with 5 gallons, we need to add 0.71 gallons of water to dilute the gravity and reach the target of 1.056.